This application is related to co-pending application Ser. No. 482,884 filed on Apr. 7, 1983 by Matsumura et al, and assigned to Nipondenso Co. Ltd. and another co-pending application Ser. No. 501,789 titled "Fuel Injection Pump Having a Compact Spill-Port Timing Control Unit" filed on June 7, 1983 by the same inventors as the present application and assigned to Nippondenso Co. Ltd.
This invention relates generally to fuel injection for internal combustion engines, and more particularly, the present invention relates to apparatus and method for controlling amount of fuel injected by a fuel injection pump of distribution type.
In conventional fuel injection pumps of distribution type which are used mainly for diesel engines, the fuel flow is controlled by changing an effective compressing stroke of a plunger of the pump by moving axially a ring-like member, which selectively opens a spill port, by way of a mechanical governer. However, when it is intended to electronically control the amount of fuel supplied to the engine, the position of the ring-like member has to be accurately and precisely controlled when such a conventional fuel injection pump is employed. Accordingly, such an electronically controlled fuel injection pump requires a high-grade actuator, a position sensor and the like, resulting in complex structure and high manufacturing cost.
A new type fuel injection pump was divised in order to remove such drawbacks. This new fuel injection pump does not employ the above-mentioned ring-like member or high-grade actuator, but comprises an electromagnetic valve which makes compressed fuel spill or escape to terminate fuel injection. Such a new fuel injection pump comprising an electromagnetic valve is disclosed in U.S. Pat. No. 3,880,131.
According to such a new fuel injection pump, however, the valve-closing duration, for which the spill port is being blocked, has not been necessarily controlled in a desired manner, and therefore, the amount of fuel cannot be satisfactorily controlled.